Centrifugal switch



Nov. 15, 1966 P. KRUPEN 3,286,057

CENTRIFUGAL SWITCH Filed May 6, 1964 F IG. 4

INVENTOR. PHILIP KRUPEN BY-' I fi M p -411? .4 TTOR NE Y5.

United States Patent Ofifice 3,286,057 CENTRIFUGAL SWITCH Philip Krupen,Silver Spring, Md., assignor to the United States of America asrepresented by the Secretary of the Army Filed May 6, 1964, Ser. No.365,540 2 Claims. (Cl. ZOO-80) The invention described herein may bemanufactured and used for or by the Government of the United States ofAmerica for governmental purposes without the payment to me of anyroyalty thereon.

This invention relates to an improved centrifugal switch and moreparticularly to an improved safety switch for arming rotating artilleryshells.

Centrifugal switches are well known and are used in many types ofrotating equipment and machinery. However, they are perhaps best knownfor their use as arming switches in rotation projectiles and especiallyin artillery shells. The switches are used in conjunction with impact,proximity, and other types of fuzes to keep the projectile disarmed ordisabled until such a time as the projectile is subject to substantialradial or centrifugal forces during inflight rotation. When used in thismanner, the centrifugal switches are safety devices preventing prematuredetonation of the projectile and very often are used to maintain a shortacross the squib or detonating mechanism of the projectile until suchtime as the projectile is fired. In other arrangements, the switch is inseries with the detonating mechanism of the projectile and presents anopen circuit until the projectile is launched.

Both series and shunt type centrifugal switches have been providedutilizing an inertial mass sometimes in the form of a plunger or pistonbiased by a spring inwardly of the switch and adapted to move outwardlythrough a suitable cylinder or chamber to either open or close a circuitas the case may be. The inward bias force of the spring isconventionally overcome only by the substantial forces to which theswitch is subjected when the projectile, i.e. an artillery shell, isfired.

Both the known series and shunt type centrifugal switches suffer fromthe serious disadvantage that breakage which may be caused by droppingthe switch during handling, or other serious malfunction of the unit,may render the switch either completely incapable of disarming theprojectile or subsequently properly arming it. For example, in switchesincorporating a frangible element, if the switch is dropped and thefrangible element broken prior to firing the projectile, even theslightest mis-alignment or malfuuction may render the switch completelyincapable of preventing premature detonation of the projectile charge.

The present invention avoids the abovementioned difficulties byproviding a very simple, inexpensive centrifugal switch incorporating adouble safety feature which very significantly reduces the possibilityof switch malfunction. The switch of the present invention presents, ineffect, two separate and completely independent switches in series, bothof which must be closed to arm a projectile. This added safety featureis obtained while at the same time maintaining the overall simplicity,small-size, and reliability of operation so necessary to a satisfactoryartillery shell switch.

It is therefore one object of the present invention to provide a novelcentrifugal switch.

Another object of the present invention is to provide an improved safetyswitch.

Another object of the present invention is to provide an improved armingdevice for rotary projectiles.

Another object of the present invention is to provide 3 ,286,057Patented Nov. 15, 1966 an improved series type centrifugal switch havinga double switch closure safety feature.

Another object of the present invention is to provide an improveddetonating circuit for rotary type projectiles.

These and further objects and advantages of the invention will be moreapparent upon reference to the following specification, claims andappended drawings wherein:

FIGURE 1 is a perspective view showing the simplified centrifugal switchof the present invention.

FIGURE 2 is a cross section through the switch of FIGURE 1 in the restor open circuit position.

FIGURE 3 is a cross section similar to FIGURE 2, showing the switchelements moved to the closed position under the influence of centrifugalforces; and

FIGURE 4 shows a projectile fuze incorporating the switch of the presentinvention.

Referring to the drawings, the novel centrifugal switch of thisinvention generally indicated at 10 comprises a cylindrical casing 12preferably of circular cross sectional configuration and formed ofelectrically conductive material such as brass. As illustrated in FIGURE1, the switch 10 is adapted to be rotated in an artillery shell or otherrotating device about a vertical axis 14 passing through the center ofthe switch and perpendicular to its longitudinal axis in a directionindicated by the arrow 16.

Cylindrical casing 12 as illustrated in FIGURE 2 and 3 is provided ateach end with a circular cylindrical chamber 18 and 20 extending fromeach end of the casing almost to the center line or rotational axis 1-4.The inner ends of the chambers 18 and 20 are separated by a solidcentral portion 22 defining inner ends 24 and 26 for the chambers whilethe outer ends of the chambers are provided with flanges 27 and 29closed off by annular in sulating discs or plugs 28 or 30. Imbeddedwithin and received through the plugs 28 and 30 are a pair of electricalleads or contacts in the form of conductive metal rods 32 and 34.

Slidably received within the chambers 18 and 20 are a pair of inertialmasses in the form of electrically conductive slugs or pistons 36 and 38biased radially inwardly of the device by a pair of coil springs 40 and42. The radially outer ends of the pistons 36 and 38 are provided withreduced diameter portions or bosses 44 and 46 over which the inner endsof the coil springs are received so that the inner ends of the springsbear against the pistons while the outer ends of the springs bearagainst the flanges 27 and 29. The pistons may, if desired, bepositioned against the inner ends 24 and 26 of the chambers by stops 48and 50.

FIGURE 2 shows the normal or open circuit position of the switch withthe pistons 36 and 38 biased against the inner ends of the chambers bythe coil springs 40 and 42. When the switch is rotated so that thepistons 36 and 38 are subjected to centrifugal forces as illustrated bythe arrows 52 and 54 in FIGURE 3 the pistons slide through the chambers18 and 20, compressing the springs 40 and 42 until the bosses 44 and 46engage the inwardly projecting ends of the electrical leads 32 and 34.At this time, a circuit is completed from lead 32 by way of piston 36,electrically conducting casing 12 and piston 38 to the other lead 34. Ifeither of the pistons 36 or 38 does not engage its respective lead, thenthe circuit is not completed.

FIGURE 4 illustrates in dashed lines a. projectile 60 such as a rotaryartillery shell incorporating the novel switch 10 of this invention. InFIGURE 4 the switch is shown as connecting a power supply represented bythe battery 62 through a proximity or other detonating device 64 to thesquib or firing element 66 of the projectile. As can be seen, thepistons 36 and 38 which are similarly numbered in FIGURE 4 provide twoseparate and completely independent switches in series, both of whichmust be closed to complete the circuit from the battery 62 through thefuze to the squib 66. If either one of these switches is not closed,actuation of the device 64 will not fire the squib.

As can be seen from the above, the present invention provides a novelswitch and projectile firing circuit having improved safety featuresover prior constructions While at the same time maintaining theextremely small size and minimum of complexity particularly suited forincorporation in projectiles. The rotational speed at which switchclosure occurs may be adjusted as desired, and is a function of the massof the pistons 36 and 38, the stiltness of the springs 40 and 42, thedistance of travel of the pistons, and other factors such as thefrictional resistance between the pistons and the walls of the chambers.While it is normally not necessary, the ends of the springs 40 and 42may be conductively secured to the walls of the chambers and to thepistons so as to insure continuous electrical contact between thepistons and the casing 12 through the springs. The circuit of FIGURE 4cannot be completed even if the switch is dropped and one of the springsbroken since both pistons must move completely through the chambers andengage the leads or contacts 32 and 34 to complete the circuit.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States LettersPatent is:

1. A centrifugal switch comprising an electrically conductive casinghaving a pair of radial chambers on diametrically opposite sides of arotational axis passing through the center of said casing, an insulatingplug closing ofi the radial outer ends of each of said chambers, aconductive metal rod fixedly imbedded in and passing completely througheach of said plugs, a conductive piston slidable in each of saidchambers and electrically coupled to said casing, and coiled springmeans biasing said pistons radially inward of said casing away from saidmetal rods.

2. A centrifugal switch according to claim 1 including a separate coiledspring in each of said chambers. each of said springs bearing at one endagainst one of said pistons and at the other end against said housing atthe closed end of said chambers.

References Cited by the Examiner UNITED STATES PATENTS 1,896,798 2/1933Leslie 200- 2,584,983 2/1952 Butterworth 20080 X 2,712,791 7/1955Bleakney et a1 10279 X 2,900,909 8/1959 Jordan 102-702 3,035,521 5/1962Hynard 102-79 X 3,181,466 5/1965 Czajkowski 102--70.2

BENJAMIN A. BORCHELT, Primary Examiner.

G. H. GLANZMAN, Assistant Examiner.

1. A CENTRIFUGAL SWITCH COMPRISING AN ELECTRICALLY CONDUCTIVE CASINGHAVING A PAIR OF RADIAL CHAMBERS ON DIAMETRICALLY OPPOSITE SIDES OF AROTATIONAL AXIS PASSING THROUGH THE CENTER OF SAID CASING, AN INSULATINGPLUG CLOSING OFF THE RADIAL OUTER ENDS OF EACH OF SAID CHAMBERS, ACONDUCTIVE METAL ROD FIXEDLY IMBEDDED IN AND PASSING COMPLETELY THROUGHEACH OF SAID PLUGS, CONDUCTIVE PISTON SLIDABLE IN EACH OF SAID CHAMBERSAND ELECTRICALLY COUPLED TO SAID CASING, AND COILED SPRING MEANS BIASINGSAID PISTONS RADIALLY INWARD OF SAID CASING AWAY FROM SAID METAL RODS.